U.S. patent application number 12/032805 was filed with the patent office on 2008-09-18 for molded beam for optoelectronic sensor chip substrate.
Invention is credited to Robert S. Stricklin.
Application Number | 20080224334 12/032805 |
Document ID | / |
Family ID | 39761846 |
Filed Date | 2008-09-18 |
United States Patent
Application |
20080224334 |
Kind Code |
A1 |
Stricklin; Robert S. |
September 18, 2008 |
Molded Beam for Optoelectronic Sensor Chip Substrate
Abstract
A substrate on which a plurality of epoxy over molded integrated
circuit dies are formed includes a beam formed on the substrate for
providing stiffness to the substrate. The beam includes structure
having a cross-sectional shape, for example, substantially in the
shape of a trapezoid, "T" or "L", and may be formed on the top or
bottom surface of the substrate.
Inventors: |
Stricklin; Robert S.;
(Richardson, TX) |
Correspondence
Address: |
Locke Lord Bissell & Liddell LLP;Attn: Michael Ritchie, Docketing
2200 Ross Avenue, Suite # 2200
DALLAS
TX
75201-6776
US
|
Family ID: |
39761846 |
Appl. No.: |
12/032805 |
Filed: |
February 18, 2008 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
60891238 |
Feb 23, 2007 |
|
|
|
Current U.S.
Class: |
257/793 ;
257/E21.502; 257/E23.119; 438/114 |
Current CPC
Class: |
H01L 24/48 20130101;
H01L 2924/14 20130101; H01L 24/45 20130101; H01L 2224/48091
20130101; H01L 2224/45144 20130101; H01L 2924/181 20130101; H01L
2224/45144 20130101; H01L 2224/97 20130101; H01L 2924/01033
20130101; H01L 2224/97 20130101; H01L 21/56 20130101; H01L
2924/01079 20130101; H01L 2924/00015 20130101; H01L 2924/00014
20130101; H01L 2924/00012 20130101; H01L 2924/00 20130101; H01L
2224/48091 20130101; H01L 2224/85 20130101; H01L 2924/00 20130101;
H01L 2224/48465 20130101; H01L 23/3121 20130101; H01L 24/97
20130101; H01L 2924/181 20130101; H01L 2224/48465 20130101; H01L
2924/14 20130101; H01L 2224/48091 20130101 |
Class at
Publication: |
257/793 ;
438/114; 257/E21.502; 257/E23.119 |
International
Class: |
H01L 23/29 20060101
H01L023/29; H01L 21/56 20060101 H01L021/56 |
Claims
1. A substrate on which a plurality of epoxy over molded integrated
circuit dies are formed including: an epoxy formed beam molded on
the substrate for providing stiffness to the substrate.
2. The substrate of claim 1 wherein said beam has a cross-sectional
shape substantially in the form of a trapezoid.
3. The substrate of claim 1 wherein said beam has a cross-sectional
shape substantially in the form of the letter "T":
4. The substrate of claim 1 wherein said beam has a cross-sectional
shape substantially in the form of the letter "L".
5. The substrate of claim 1 wherein the substrate has a top surface
and a bottom surface, and said beam is formed on said top
surface.
6. The substrate of claim 1 wherein the substrate has a top surface
and a bottom surface, and said beam is formed on said bottom
surface.
7. The substrate of claim 1 wherein said beam is formed on said top
surface of said substrate adjacent to the over molded dies.
8. A process for fabricating an electronic circuit component
comprising: forming on a substrate, a plurality of component
packages wherein each package includes a plurality of integrated
circuit dies; forming wire bonds attached to the dies; over molding
the dies and bonds using an epoxy material; forming a beam using
epoxy material on the substrate; and cutting the over molded dies
from the substrate to form individual component packages
9. The process of claim 8 wherein the beam is formed having a
cross-sectional shape substantially in the form of a trapezoid.
10. The process of claim 8 wherein the beam is formed having a
cross-sectional shape substantially in the form of the letter
"T".
11. The process of claim 8 wherein the beam is formed having a
cross-sectional shape substantially in the form of the letter
"L".
12. The process of claim 8 wherein the beam is formed on the
substrate adjacent to the over molded dies.
Description
RELATED APPLICATION
[0001] The present application claims the benefit of U.S.
Provisional Patent Application Ser. No. 60/891,238 filed Feb. 23,
2007 entitled "Molded Beam for Optoelectronic Sensor".
TECHNICAL FIELD OF THE INVENTION
[0002] The present invention relates to integrated circuits, and
more particularly to integrated circuit fabrication.
BACKGROUND OF THE INVENTION
[0003] Integrated circuits such as, for example, optoelectronic
sensors, are typically manufactured as packages in multiple
quantities formed from "chips" fabricated on printed circuit
boards. These packages are constructed by forming integrated
circuit dies on a FR4 printed circuit board or
Bismaleimide-Thriazine (BT) substrates. The die is wire bonded
with, for example, gold wire and then over molded with epoxy to
protect the die and the wire bonds. The substrate is then cut into
small pieces using a sawing process to form individual integrated
circuit packages.
[0004] The over mold process utilizes a transfer molded epoxy
material. The epoxy material and the substrate on which the
integrated circuit dies are formed, have different thermal
coefficient of expansions. The combination of the epoxy material
and the substrate and the tooling design methods utilized, create
large stresses in the individual integrated circuit packages.
Stresses in the individual packages are caused by the difference in
thermal coefficient of expansion between the mold epoxy and the
substrate. The stresses cause the substrate to curl after over
molding. As a result of the curling, fixturing is necessary to
flatten the substrate prior to the sawing operation.
[0005] A need has thus arisen for a substrate and fabrication
process which provides additional strength for the substrate to
prevent undesired curling of the substrate prior to a sawing
operation.
SUMMARY OF THE INVENTION
[0006] In accordance with the present invention, a substrate on
which a plurality of epoxy over molded integrated circuit dies are
formed includes a beam formed on the substrate for providing
stiffness to the substrate. The beam includes structure having a
cross-sectional shape, for example, substantially in the shape of a
trapezoid, "T" or "L", and may be formed on the top or bottom
surface of the substrate.
BRIEF DESCRIPTION OF THE DRAWINGS
[0007] For a more complete understanding of the present invention
and for further advantages thereof, reference is now made to the
following Description of the Preferred Embodiments taken in
conjunction with the accompanying Drawings:
[0008] FIG. 1 is a pictorial illustration showing a plurality of
dies on a substrate;
[0009] FIG. 2 is a pictorial illustration showing epoxy over molded
dies on a substrate;
[0010] FIG. 3 is a pictorial illustration showing use of the
present beam molded on the top surface of a substrate;
[0011] FIG. 4 is a pictorial illustration showing an individual
component severed from a substrate;
[0012] FIG. 5 is a pictorial illustration of an alternate
embodiment of the present beam;
[0013] FIG. 6 is a pictorial illustration of an alternate
embodiment of the present beam; and
[0014] FIG. 7 is a pictorial illustration of the present beam
formed on the bottom surface of a substrate.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0015] Referring to the FIG. 1, a plurality of individual
integrated circuit dies 10 are shown fabricated on a substrate 12,
having a top surface 12a and a bottom surface 12b (FIG. 7).
Substrate 12 may comprise, for example, a FR4 or BT substrate. Dies
10 are wire bonded utilizing wires 14.
[0016] FIG. 2 illustrates dies 10 and wires 14 being over molded
with epoxy 18 to form integrated circuit packages 16. Epoxy 18 may
comprise for example, thermoset epoxy plastic molding compound
materials.
[0017] Referring now to FIG. 3, an embodiment of the present
stiffening beam 22 is illustrated. Beam 22 is formed having a
cross-sectional shape substantially in the form of the letter "L",
and is formed on top surface 12a of substrate 12 adjacent to
packages 16. Beam 22 is formed from the same epoxy 18 which over
molds dies 10 and wires 14. Beam 22 adds sufficient strength to
stabilize substrate 12 thereby preventing substrate 12 from curling
prior to the saw operation. Beam 22 is formed in the fabrication
process at about the same time as the over molding process of dies
10 takes place.
[0018] FIG. 4 illustrates a single package 20 after the sawing
operation which severs packages 16 from substrate 12. During the
sawing operation, beam 22 is discarded.
[0019] FIGS. 5 and 6 illustrate additional embodiments of the
present beam. FIG. 5 illustrates a beam 24 having a cross-sectional
shape substantially in the form of a trapezoid. FIG. 6 illustrates
a beam 25 formed having a cross-sectional shape substantially in
the form of the letter "T".
[0020] FIG. 7 illustrates the use of beam 22 formed on bottom
surface 12b of a substrate 12.
[0021] Other alterations and modifications of the invention will
likewise become apparent to those of ordinary skill in the art upon
reading the present disclosure, and it is intended that the scope
of the invention disclosed herein be limited only by the broadest
interpretation of the appended claims to which the inventors are
legally entitled.
* * * * *